1. Field of the Invention
The field of the invention is that of communication between terminals within a network, more particularly the field of controlling resources of any type (radio, optical, mechanical (in particular acoustic), or electrical (analog) resources) offered by base stations of a network.
In the present context, the term “terminal” refers to any network equipment, and in particular any user equipment, such as fixed or mobile computers, mobile telephones, and servers.
2. Description of the Prior Art
The person skilled in the art knows that a communication network (or installation) generally comprises a core network (CN) coupled to one or more nodes each coupled via an interface to one or more base transceiver stations, each associated with one or more cells each covering an area, for example a radio area, in which one or more user equipments such as mobile telephones may be located. These nodes are known as base station controllers (BSC) in 2G and 2.5G networks such as GSM and GPRS networks or as radio network controllers (RNC) in 3G networks such as UMTS networks. Also, base stations are known as base transceiver stations (BTS) in a GSM or GPRS network and a Node B in a UMTS network.
In UMTS networks, for example, the RNCs control the Nodes B, and in particular manage their radio resources, and control the terrestrial transfer of traffic between the core network and the Nodes B, via a Iub interface. To be more precise, the Iub interface comprises a stack of protocols divided between different network elements (RNCs and Nodes B), as shown in FIG. 1.
With regard to the frame portion to be transmitted at the radio (Uu) interface, the portion of the protocol stack managing the Iub interface implemented in a Node B comprises a frame protocol (FP) module with a number of functions, in particular that of transporting at the Iub interface transport blocks (i.e. blocks of radio frames that are then transmitted or received by the radio modem (or physical layer (PHY) of the Node B), transporting power control (outer loop) information from the RNC to the Node B, supporting transport channel synchronization mechanisms, supporting Node B synchronization mechanisms, and transferring parameters from the radio interface of the RNC to the Node B.
The portion of the protocol stack implemented in a Node B comprises two subsystems for controlling communication with terminals at the Uu interface.
A first subsystem manages the broadcast control channel (BCCH). To this end, a portion of layers 2 and 3 of the radio interface is implemented in the Node B, in particular radio resource control (RRC-b), radio link control (RLC-b), and medium access control (MAC-b) portions. The Node B can therefore, firstly, insert into the system blocks of the BCCH the information relating to certain radio parameters of the cells that it manages (RRC-b function), secondly, segment the system information blocks into transport blocks (RLC-b function), and, thirdly, handle BCCH scheduling (MAC-b function).
A second subsystem manages the Node B. It comprises the Node B Application Part (NBAP) protocol, which has a number of functions, in particular managing the configuration of the cells, which enables the RNC to manage the cell configuration information under the control of the Node B, to manage common transport channels, which enables the RNC to configure said channels, to manage “resource” events, which enables the Node B to inform the RNC of the status of its radio resources, and to align the configuration, which enables the RNC and the Node B to verify that they hold the same radio resource configuration information, and where applicable to coordinate that information.
The above networks are entirely satisfactory in the standard mode of operation, i.e. when data is exchanged between the core network and the user equipments. On the other hand, if it is required to connect to this type of network a traffic source other than those already constituting the user equipments and the core network, for example via a satellite link, even if only momentarily, this must be effected at the level of the Iub interface between the node (RNC) and the base station(s) (Node(s) B) concerned. This causes a number of problems. Similar problems arise if it is required to transfer traffic directly to a base station (Node B) and from a core network without going via the RNC, even if only momentarily, or when it is required to use a satellite link to transmit traffic, for example, rather than the conventional terrestrial link (this is known as “backhauling via satellite”).
The above problems include in particular the increase in the transmission time-delay to the base station (Node B), which seriously interferes with the operation of the algorithms for managing resources, for example radio resources (allocation of codes, power control, handover, and the like), and which is reflected in a degraded quality of service. This problem is particularly severe in the case of backhauling via satellite.
There are also the problems of controlling the resources, for example radio resources, of the base station (Node B), of programming the physical layer (PHY) and of “level 2” protection, which functions are situated in the node (RNC) and whose associated protocol is operative at the Iub interface. Inserting a new traffic source, for example via a satellite link, would necessitate the installation in the satellite link of the functions of the Iub interface, which would amount to coupling the base station(s) (Nodes(s) B) to an additional interface. However, for the portion controlled by the RNC, the architecture of the Universal Terrestrial Radio Interface Network (UTRAN) allows management of Nodes B only via a single Iub interface.
There is also the problem of controlling synchronization of the reference clock of the channels under the control of the base stations (Nodes B). This problem is particularly serious if the base stations are used as terrestrial repeaters, for example within a data broadcasting installation, in particular a satellite installation. In this type of installation, the satellite transmits the same traffic on a first frequency fMSS and a second frequency fFSS respectively to user equipment (UE) in the cells managed by the base stations (Nodes B) and to said base stations, which relay said received traffic to the user equipments concerned on the frequency fMSS. As a result of this the user equipments can receive the same traffic twice on the same frequency fMSS, but offset in time, which generates conflicts.
Thus an object of the invention is to cure some or all of the drawbacks previously cited.